Ba-deficiency in BaCoO3 cathode allows high performance for proton-conducting solid oxide fuel cells

Abstract

A slight deficiency of Ba in BaCoO3 boosts its performance as the cathode for proton-conducting solid oxide fuel cells (H–SOFCs). The Ba-deficiency compound Ba0.95CoO3 is successfully prepared, and the Ba-deficiency is found to be beneficial for the improvement in chemical stability. Theoretical calculations at the atomic level reveal that the Ba-deficiency in BaCoO3 improves the protonation of the material and also lowers the energy barriers in the proton migration procedure. Furthermore, surface catalytic activity towards O2 is enhanced with the Ba-deficiency, allowing a weakened O–O bond. The theoretical predictions have been proved with experimental studies. The cell using the traditional BaCoO3 cathode shows a peak power density of 720 mW cm-2 at 700 °C, while the peak power density of the Ba0.95CoO3 cell is 1155 mW cm-2 at the same testing condition. Impedance analysis indicates that the much-reduced polarization resistance contributes to the enhanced fuel cell performance. The current Ba0.95CoO3 cell shows not only improved performance compared with the stoichiometric BaCoO3 cell but also exhibits comparable or even better performance than some of the recently reported high-performance H–SOFCs, suggesting the Ba-deficiency strategy provides a facile and interesting way to tailor the traditional cathode materials with high performance.